Aromatic amino acids and short peptides containing phenylalanine (Phe) have been demonstrated to increase the minimum gelling concentration and/or solubility of deoxy-hemoglobin-S in aqueous solution. However, these compounds do not readily cross the intact red blood cell membrane under usual conditions of incubation. To investigate the role of Phe and tryptophane (Trp) as potential antisickling agents in intact human red blood cells (RBCs), a liposomal transport system has been developed to transfer Phe or Trp into intact SS-RBCs. Washed RBCs from patients with sickle cell anemia are incubated with either phe or trp loaded small unilamellar liposomes resulting in millimolar incorporation of Phe or Trp. Percent sickling of oxygenated and deoxygenated SS-RBCs after amino acid incorporation via liposomes is measured following fixation with deoxygenated phosphate-buffered-gluteraldehyde by microscopic examination with Nomarski interference optics. Incorporation of Phe or Trp into oxy- and deoxy-SS-RBCs respectively, via liposomal transport system markedly inhibit, and reverse respectively, the "in vitro" sickling of deoxy Hb-S. These findings raise the possibility that a nontoxic liposomal transport system which facilitates incorporation of antisickling agents may have significant therapeutic implications in the treatment of sickle cell disease. The proposed research will provide the scientific background necessary for the eventual clinical use of amino acid or peptide incorporate liposomes in the treatment of sickle cell disease. The goals of this investigations are: To perform extensive studies on the transport of short peptides into intact SS-RBCs via liposomal transport system; To optimize and standardize the amino acid incorporation procedure; and To evaluate the viability and to study the effect of amino acid or peptide incorporation on the metabolic, functional and rheological properties of SS-RBCs. Finally survival of RBCs treated with amino acid or peptide loaded liposomes will be studied in rabbits.